<!doctype html>
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<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
            font-size: 13px;
            list-style: none;
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        .menu {
            width: 210px;
            margin: 50px auto;
            border: 1px solid #ccc;
        }

        .menu p {
            height: 25px;
            line-height: 25px;
            font-weight: bold;
            background: #eee;
            border-bottom: 1px solid #ccc;
            cursor: pointer;
            padding-left: 5px;
        }

        .menu div ul {
            display: none;
        }

        .menu li {
            height: 24px;
            line-height: 24px;
            padding-left: 5px;
        }
    </style>
    <script type="text/javascript">
        window.onload = function () {
            var menu = document.getElementById('menu'),
                    ps = menu.getElementsByTagName('p'),
                    uls = menu.getElementsByTagName('ul');
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                ps[i].id = i;
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                    } else {
                        u.style.display = 'block';
                    }
                }
            }
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    </script>
</head>
<body>
<div class="menu" id="menu">
    <div>
        <p>Web前端</p>
        <ul style="display:block">
            <li>JavaScript</li>
            <li>DIV+CSS</li>
            <li>jQuery</li>
        </ul>
    </div>
    <div>
        <p>后台脚本</p>
        <ul>
            <li>PHP</li>
            <li>ASP.net</li>
            <li>JSP</li>
        </ul>
    </div>
    <div>
        <p>前端框架</p>
        <ul>
            <li>Extjs</li>
            <li>Esspress</li>
            <li>YUI</li>
        </ul>
    </div>
</div>
</body>
</html>
